Editors' Choice

Science  04 Jan 2008:
Vol. 319, Issue 5859, pp. 13


    The massive volcanic eruption of Santorini just before about 1600 BCE, or 3600 years ago, is one of the largest historical eruptions. It spread ash across the central Mediterranean and formed a massive caldera in the island of Thera. Despite its size, the scale of its effects on surrounding nascent civilizations even nearby in Crete continues to be debated. Bruins et al. now provide evidence that the eruption may have spawned a tsunami that devastated the northern coast of Crete, including a major city of the early Minoan civilization. They identified several deposits along the coast and in the ancient city of Palaikastro that include chaotic mixtures of ash, pebbles, fragments of walls and buildings, Minoan pottery, bones, and other debris. The geochemistry of the ash ties it to Santorini, and the position and stratigraphy of the debris layer are consistent with deposition by overwash in a tsunami. The highest debris implies that the height of the waves reached at least 9 m above sea level, but models of a tsunami and the extent of devastation are consistent with a much higher wave height, perhaps up to 35 m, that would have overwhelmed coastal cities. — BH

    J. Archaeol. Sci. 35, 191 (2008).


    Two Speeds at Once

    In the seemingly never-ending quest to speed up data transfer, light constitutes the ultimate communications carrier. However, the speed of light through a medium is generally constant, making photon storage and on-chip optical signal processing difficult tasks to implement. To slow things down, coupling microring resonators to an optical waveguide can effectively delay the propagation of photons. It has also been shown that the dispersion properties of these devices can distort the pulse profile so that the speed of light appears to be exceeded, providing so-called fast-light. From a practical viewpoint, it would be desirable to combine both of these properties in a single optical device. Recent work has found that these microring resonators are birefringent with respect to the polarization of the propagating light; i.e., one polarization simultaneously propagates faster than its orthogonal counterpart. From calculations, Fietz and Shvets show that by using light of mixed polarization and adjusting the mixing angle of that light and the number of microring resonators along the waveguide, a tunable delay time between polarized wave packets of incoming light should be readily achieved. — ISO

    Opt. Lett. 32, 3480 (2007).


    Live Fast, Die Young

    Classically, the short stature of human pygmies was thought to confer a selective advantage for forest life or to provide greater resistance to starvation, but not all pygmy groups are forest dwellers or short of food. In an investigation of the Aeta, a Philippine pygmy group with a life expectancy at birth of only 16.5 years, Migliano et al. discovered that young women stop growing between the ages of 12 and 13, and that their reproductive fitness peaks at 15 years of age when they have attained an average height of 140 cm. By comparison to a similarly nourished group, the Turkana women of East Africa start reproducing at an average age of 22 years. At birth, Turkana women can expect to survive 48 years, and by 18 to 19 years have reached an average adult height of 166 cm. Although larger adult size results in fertility gains and greater child survival, for a pygmy anywhere in the world, it appears to be too risky to wait; instead, it seems to pay to grow up fast and have babies before disaster hits. Whether this is a consequence of unusual burdens of infectious disease or vulnerability to other, as yet unknown, hardships, it remains unclear why pygmies have such low life expectancies. — CA

    Proc. Natl. Acad. Sci. U.S.A. 104, 20216 (2007).


    Dividing the Inheritance

    Cell division can be a hazardous process for any cell that needs to segregate the two copies of its genome into daughter cells. Prokaryotic cells often harbor extrachromosomal elements, such as plasmids, that also need to be allocated fairly. One well-studied example is the partitioning of the R1 multidrug resistance plasmid in Escherichia coli; this process is powered by the actin-like ATPase ParM. Although ParM has structural homology to actin, in filamentous form, it displays dynamic instability reminiscent of microtubules. Campbell and Mullins have used time-lapse fluorescence microscopy to follow plasmid segregation in E. coli. ParM filaments form spindles that are capable of capturing a plasmid at each end and then pushing them to opposite ends of the cell at about 50 nm/s. Initially, spindles do not always align with the long axis of the cell, but alignment probably occurs during elongation. After reaching the poles, the filaments undergo catastrophic depolymerization. Remarkably, the relocated plasmids do not remain fixed at the poles, and may diffuse and suffer multiple rounds of segregation before cell division. — VV

    J. Cell Biol. 179, 1059 (2007).